Reasons why water and wind erosion are diffrent.
2 answers:
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Answer:
The minimum average speed the opponent must move so that he is in position to hit the ball is approximately 5.79 m/s
Explanation:
The given parameters of the ball are;
The initial speed of the ball = 15 m/s
The direction in which the ball is launched = 50° above the horizontal
The location of the other tennis player when the ball is launched = 10 m from the ball
The time at which the other tennis player begins to run = 0.3 seconds after the ball is launched
The height at which the ball is hit back = 2.1 m above the height from which the ball is launched
The vertical position, 'y', at time, 't', of a projectile motion is given as follows;
y = (u·sinθ)·t - 1/2·g·t²
When y = 2.1 m, we have;
2.1 = (15·sin(50°))·t - 1/2·9.8·t²
∴ 4.9·t² - (15·sin(50°))·t + 2.1 = 0
Solving with the aid of a graphing calculator function, we get;
t = 0.199776187257 s or t = 2.14525782198 s
Therefore, the ball is at 2.1 m above the start point on the other side of the court at t ≈ 2.145 seconds
The horizontal distance, 'x', the ball travels at t ≈ 2.145 seconds is given as follows;
x = u × cos(50°) × t = 15 × cos(50°) × 2.145 ≈ 20.682 m
The horizontal distance the ball travels at t ≈ 2.145 seconds, x ≈ 20.682 m
Therefore, we have;
The time the other player has to reach the ball, t₂ =2.145 s - 0.3 s ≈ 1.845 s
The distance the other player has to run, d = 20.682 m - 10 m = 10.682 m
The minimum average speed the other player has to move with, = d/t₂
∴ = 10.682 m/(1.845 s) ≈ 5.78970189702 m/s ≈ 5.79 m/s
The minimum average speed the opponent must move so that he is in position to hit the ball, ≈ 5.79 m/s.
The final kinetic energy of the ball is 2.45 J
Explanation:
We can solve this problem by using the law of conservation of energy.
In absence of frictional effect, the mechanical energy of the apple must be conserved during the fall. So we can write:
where :
is the initial potential energy, at the top
is the initial kinetic energy, at the top
is the final potential energy, at the bottom
is the final kinetic energy, at the bottom
By explicing the potential energy, we can rewrite the equation as:
where:
m = 0.5 kg is the mass of the apple
is the acceleration of gravity
is the initial height
is the final height
The initial kinetic energy is zero, since the ball starts from rest:
Therefore we can solve the equation for , the final kinetic energy of the ball:
Learn more about kinetic energy and potential energy:
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